#5.1 Java Tutorial | Array 1D | 2D | Jagged Array

Oh [Music] so once we have seen the theory of a day so we have talked about one dimension a day we have talked about two dimensional array and why we even need an a day because if you have multiple elements and you want to ensure storing those elements in two different variables we can use one common variable where you can store all the values so let's try to implement that in a practical scenario here so let's say I want to create an array of integers so I would simply say I have to say integers ain't I mean I will use end of nums equal to in Java added an object so we have to use a new keyword and we'll use a int to specify the size of an array let's say I want an array of four elements now it is composite to define the size of an array because if you miss to define the size of an array it will give you error now once you say for this size is fixed as soon as you write this line so inside your inside your JVM you can see in your heap memory something happens in this way so inside your heap memory you got this you got this box where you have these four boxes so the first box will have 0 in fact all the boxes will have 0 is because since we are getting adding of int so if you create or adding like that it will create add it off and with all the values as 0 just to prove my point what I will do is I will I will print the values so if I want to print the values I would simply say system dot out dot println let me pick up any value so let's say I want to pick up the third box there the third box index number would be too because index number starts with 0 right so you can see the first box is 0 then we have 1 then we have 2 then we have 3 so I want to fetch the third box which is this - which is - right so if you if you write - you'll be getting the output which is say we are getting 0 now why 0 is because the the value by default is 0 now let's I don't want the values to be 0 I want my own values there so what we can do is we can specify the values individually here so we can say in nums of 0 i want to assign the value let's say 8 then we can say num start 1 we can specify 12 we can say nums of 2 we can specify 76 and I mean any value will do here I'm just specifying the values so if I say 3 let's say 54 just to have that all numbers not in sequence so we have 812 for 76 and 54 so we have all this numbers and you're fetching only two here so if I fetch two it will of course give you 76 right because we are fetching the value of this second element which is of course I mean third element which is in terms of two so we called 76 now we can also change the value I mean we can change the value right once you define it we can also change it we can say nums of two we can again change the value because anyway this array is variable right so you can change the values of it so as soon as I write this line I mean after this line you can see the box there it has value eight 12 76 and 54 but as soon as you line write this line you can you can see the change there so now 76 becomes 99 and that's why when you fetch this value it will give you 99 simple but what will happen if I try to print so let's say I don't have I don't have a value at forth location because the size of my array is 4 and I'm trying to access the fifth location now and you can see outside the box we have nothing so I put on this code it will give you an array which is array index out of bounds exception because there is nothing nothing after that box right it only has four elements and you're trying to fetch the 5th element here so what if I assign our values to norms of 4 equal to 77 will it work now you can see while if I run this code now you can see we got the error on this line itself on line number 13 we cannot assign the value there now let's say I have assigned all the values I want to print all the values now to print all the values we have to say number of 0 then we have to say num nums of 1 then you have to say in terms of two and I'm sorry right so sure if I think four lines what we can do is we can write only one line here we can say for int I which will start with 0 because adding starts with 0 and will end I it will give a semicolon there else will say end at 4 because we have to end at 3 right so we have to say less than 4 we don't have to specify equal to sign there and then we can simply say nums of i so it will print all the values i can as you can see we got we got 8 1276 and 54 so using a for loop we can print all these all the values here in fact in the next video where we will also talk would enhance for the witches they knew not knew exactly it was it is there from a long time so we got one more way of printing the values from default from the Attic called as enhanced for-loop we'll see that later okay so this is how you use a one dimensional array so this is one D added now there's one more thing here when one when you know the value is predefined when you already know the values instead of saying new int we can also specify the value here itself we can say 8 comma 12 comma 76 comma 54 so if you know the value spree hand instead of knitting this this thing here we can directly assign the values even if I long this code now it will give the same output so that's how you can create an array one dimensional array you can print it in fact we can also create the object I mean the array of objects example if I have a class here and if I have class student' and I want to create in this student to have two things we have a roll number and we have string name what we can do is we can create multiple objects here of student we can say student s1 equal to new student that's the first object I have again we can specify the values there but let's see if I create multiple objects here if I'm creating four objects this is as true this is s3 this is s4 so if I'm creating four objects here I can create instead of that I can create the object of students I will say as I really use a square bracket then I will say new student okay I specify I have four students here and in this s in fact we can issue of writing this line we can also specify s 1 comma S 2 comma S 3 comma s4 ok so we are creating the added off students so I will recommend you to do some experiment with this you will get the exact point what I'm talking about in fact you can also apply a for loop here and you can do that also so once we got the array of student let me remove that so this is your one dimensional array and we have seen how to use it in the next we'll talk about two-dimensional arrays now once we know what is one dimensional array let's move towards two-dimensional array so just to define that what I will do is so let me create an array let's say this array is let's say a so I have this a array and which has a certain value so let's say I want to assign a value which is 1 2 3 4 so I have this array which has four values right so instead of creating 4 variables so instead of creating 4 variables I'm using one addy now let's say we have one more array which is B and the values of B is 2 comma 4 comma 6 comma 8 and then we have one more array here which is C which has let's say 5 comma 6 comma 7 comma H so these are the values I have so I have 3 arrays and we have 4 values in each receive instead of creating 4 variables I have created one array right so instead of creating 3 arrays can I create one big adding we can do that so you can see we can create a table we'll name this as D now this D is a two-dimensional array because this will this is an array which will not have simple values so D itself will have small small arrays so D will have a comma B comma C and the values of a is not just a it is so that's your first array then in the second array what we have is and the next array which you have here will have values which is 5 comma 6 comma 7 comma 8 right so we got this two-dimensional array which has array I mean we which itself has an added ok so now what if what if what if I say system dot out dot println D of 0 so when I say D of 0 it is representing the whole array here okay so Diop 0 that means the first row so you can imagine this thing as a row and column so this is first row second row third row and then we got columns so we got 1 2 5 2 4 6 these are columns so if I say D of 0 it is the whole row right so I don't want the whole row I want this second element from the first row so I can specify the second element as 1 so first row second column so we have to specify 0 comma 1 and if i underscore you get the output as - okay that's that's the way if you want to put into all the elements what we can do is we can use a for loop and now this for loop so the outer for loop we'll use this for loop for the number of rows to count a number of rows semicolon less then we have three those rights are going to use three and we say I plus plus define the number of photos and we require one more for loop there which is in J equal to zero and J less than equal to not equal to let's say I have four and then J plus plus so the inner loop will be counting the number of columns so this loop will count the number of rows and this local corner number of columns and now if I want to print so I will not use println I will only use print to specify the particular form because if I use print L then what will happen is if I specify the of I and J which will change in some time if you run this code and if you if you run this you can see we are getting all this output here I don't want output in a linear format so what I want is here it should print only in the same line with some space of course and after this inner fondo we can print a new line so that we can get the perfect structure so you can see we got one two I mean we got the same blocks here right now how exactly is walking just let's run through a loop so you can see this image we haven't added there so in this array in this box I mean we have a square box where you have three rows and four columns so all the values by default are I mean we have all the back all that if all the values there one two three four then all these values so initially when you have I and J so I value will be 0 and J value will be 0 so it will point to the first box which is 1 so it will fetch the value as 1 then the loop increments your J becomes 2 I mean J becomes 1 so it is fetching 0 1 which is the first row second element which is 2 and then your J becomes 2 it will fetch 3 your J becomes 3 it will fetch 4 now once it once you are fetching for you can see we don't have any element after that it will jump to the second row so when you say your jump into second row that means your I value now becomes 1 and then we can again your J value becomes 0 so you are fetching 2 then you can cream in increments it fetch 4 and then 6 and then 8 so that's how it will fetch all the values from 2 a dimensional array so in two-dimensional array we can have the address of same size now what if I if I change the size if what if I say this is six okay I'm not sure I mean in the first row I have four elements in the second row I have three elements and they fit in the third row let's say I have I have five elements now in this scenario since the number of columns are not fixed we cannot say for year right because the number of rows are fixed so we can say three we cannot say for year so what we'll do I will say D of I I mean for that particular row so if I say D of I so it will be either this or that will depend upon the I value I want to fetch the length of that row and it showed three year we can also say D dot line so it will give the number of rows to you so it will give number of rows I mean the number of arrays you have first add a second array throat array so it will give you three and here depend upon on which added you're working with or if you are working with the first array when your I value is 0 it will return for if your value is 1 it will return 3 when your I value is 3 it will return 5 and if I'm this code you can say this you got this type of output so this type of array where you have the number of columns are not fixed are normally called jagd arrays so if you have all the columns as same that means it is it is normal to D adding but if you have different size of the column that will be your jag daddies so the only precaution you have to take his this precaution here ok so that's it that's how you use two dimensional array and jag daddy in the next video we'll talk about enhanced for-loop so that's it thank you so much

Channel: Telusko

Views: 144,910

Keywords: telusko, navin, reddy, tutorial, java, easy, core java, free, array, 1d, 2d, multi, dimensional, jagged, define, fetch, value, from, to

Id: fuDNAKStpq0

Length: 12min 34sec (754 seconds)

Published: Thu Jan 25 2018